Elastomeric covers or sleeves and removable support core assemblies are known in the art and are particularly useful in the electrical distribution industry. The assembly is typically referred to as cold shrink tubing to differentiate it from polymeric tubing which may be shrunk by the application of heat.
FIG. 1 illustrates a typical use for, and construction of, a cold shrink tube joint or splice assembly and shows two cable-ends 11 comprising stranded conductors 12 and insulating coverings 13. The insulating covering 13 is cut away to expose an end of the conductors 12, which ends are then joined together in end-to-end configuration by suitable means 20 which may typically consist of a compressed or indented metal sleeve or a close-fitting metal tube with set-screw retainers. The joint or splice may be covered with insulating mastic or tape, omitted here for clarity of illustration.
The cold shrink tube assembly, which includes a cold shrink tube 18 in a radially expanded or stretched condition on the support core 15, is slipped over one of the cable ends prior to joining the two conductor ends to create a splice. After the splice is completed, the assembly is slid into position over the splice area and the support core is removed to permit the cold shrink tube to contract and form a tight fit around the splice. The support core 15 may be a unitary tubular core that may be a solid core helically grooved along its entire length or may be a helically wound and bonded continuous ribbon, the groove or bond line 16 permitting the support core 15 to be pulled out as a continuous strip 17 which is removed through the bore, i.e., from between the support core 15 and the cable 11. As the strip 17 is progressively withdrawn, the cold shrink tube 18 contracts around the cable as at end 19 to form a closely conforming and tightly retained protective covering.
One type of ribbon 30 includes edges 32 and 34 which interlock, as shown in FIGS. 2 and 3, when recesses 40 and 42 receive coupling projections 36 and 38 as the ribbon 30 is helically wound to form a tubular core. The interlocked edges 32 and 34 may be joined by such means as adhesives, heat welding, ultrasonic welding, or solvent welding, such that the hoop strength of the support core 15 sufficiently opposes the compressive force of the cold shrink tube 18. The hoop strength of the core is derived primarily from the strength of the ribbon 30 and secondarily by the strength of the joints that connect the ribbon 30 along the circumference of the support core 15. The joints are typically sufficiently strong so that a high force must be consistently applied to the strip 17 in order to break the joints and remove the strip 17. Repetitive motion is required to break all of the joints along the length of the support core 15 and to guide the strip 17 out of the cold shrink tube 18.
The ribbon 30 may be formed with regularly spaced perforations 44, each extending from the bottom of recess 42 through the ribbon 30 to the top of the ribbon 30. If the strength of the joints between edges 32 and 34 is high, separation of the support core 15 into the strip 17 will occur along the perforation 44. This is often not preferred because the separated perforation points can produce a rough edge on strip 17. Conversely, if the joints are not strong enough, the hoop strength of the tubular support core 15 will be too weak to support the cold shrink tube 18 and the tubular support core 15 will collapse, or “crash,” uncontrollably.